Switch system to prevent arcing of contacts



Aug. 12, 1947. M. A. SCHEG Er AL 2,425,570

SWITCH SYSTEM TO PREVENT ARCING OF CONTACTS Filed Oct. 22, 1942 FIG.1.

1 k 1 CP INVENTOR5 M Sc heg and OH .1) ic ke THEE? ATTORNEY Patented Aug. 12, 1 947 SWITCH SYSTEM TO PREVENT ARCING OF CONTACTS Marcian A. Scheg and Oscar H. Dlcke, Rochester, N. Y., assignors to General Railway Signal Company, Rochester, N. Y.

Application October 22, 1942, Serial No. 462,965

- 8 Claims.

This invention relates to circuit controlling apparatus and more particularly to apparatus controlled by and for controlling an alternating current circuit.

The problem of preventing or at least reducing sparkin upon the closure and opening of circuits has always been present and more particu larly becomes a problem where the energy for operating the contacts is small. Also, where high voltage is employed the contacts may be immersed in oil but this is not practical for low voltage circuits by reason of the contact resistance involved. This is particularly true where contacts engage each other with comparatively small contact pressures.

In view of the foregoing and other important considerations it is proposed in accordance with the present invention, which is applicable to alternating current circuits only, to employ electroresponsive circuit controlling means which closes contacts during particular portions of an alternating current cycle irrespective of the time of application of current to such electro-responsive means with respect to a cycle of such alternating current, and to so organize these contacts in a circuit structure that current cannot fiow therethrough at the instant of closure or opening thereof by reason of the relative polarity of the current at the particular time of closure or opening thereof.

Stating this more specifically it is proposed to empoly two separate contacts one of which is closed during one half-wave of an alternating current cycle and the other of which is closed during the other half-wave of an alternating current cycle and to employ one or more rectifiers in combination with these contacts so that a circuit for passing current of one polarity is closed and opened during one-half of an alternating current cycle and a branch circuit is closed and opened during the other half of such alternating current cycle. In accordance with one form of the present invention it is proposed to employ a control circuit which includes two branches in each of which there is an oppositely poled rectifier each rectifier of which has included in series therewith a contact of the special electro-responsive means which will only be closed or opened when this rectifier blocks the fiow of current as a result of which no sparking should occur because the contacts are made and broken at a, time when no current fiows therethrough.

I accordance with another form of the present invention it is proposed to employ a single rectifier and to close a circuit through the medium of one of the contacts of the special electroresponsive device at a time when such rectifier blocks the flow of current and to then shunt out this rectifier at a time when such rectifier passes the flow of current as a result or which no sparking should occur at the contacts because there is no current flowing when th first contact is closed or opened and current is bi-passed around the second contact by the rectifier at the time this second contact is either closed or opened.

Other objects, purposes and characteristic features of the present invention will be in part pointed out hereinafter in the specification and will in part beobvious from the accompanying drawings, in which:

Fig, 1 illustrates one form of the present invention; and

Fig. 2 illustrates an improved form of the present invention.

The present invention employs relays or electro-responsive devices. of very specific and special construction two forms of which have been fully described in the prior application of Scheg and Wall, Ser. No. 462,964, filed October 22, 1942, to which attention is directed for a more detailed description of this electro-responsive device.

The particular electro-responsive device such as relay CPRA shown in Fig. 1 of the drawings and described in detail in said prior Scheg and Wall application consists of a magnetizable core C of soft iron having three depending legs L L and L of which the leg L is of comparatively small cross-section. Just below and adjacent to the leg L is a fixed pivot for pivotally supporting an armature A, which armature is biased by a spring 4 to engage the leg L and which armature A upon being actuated to its active position will have its other end engage the leg L and close contact l0.

On the middle leg L of the core C is provided a winding W which winding is connected in series with a rectifier-TI through the medium of a control contact 5 of a control relay CP and a circuit including the common return connection CW to a source of alternating current, herein shown as the secondary winding of the transformer TI having its primary winding connected to an alternating current source AC. The leg L is'provided with a bucking winding H which is short-circuited for current of one polarity through the medium of the rectifier m.

Stating the operatlonbriefly, closure of the contact 5 of the control relay CP causes the winding W of the relay CPRA to be energized by its normal position to its actuated position.sothat actualclosureoffrontcontact IQ of relayCPRA does not take place until the "oil!" period of the pulsating current is well under way; In other words, the relay CPRA shown in Fig. l is constructed to begin its actuation during a substantial full pulse of positive polarity of alternating current and'to close its contact ill during a wave of negative polarity of the alternating current.

SincethewindingWoftherelayCPRAiaenengined by pulsating current, derived through the medium of the rectifier rl, suitable means must be provided to prevent chattering of the armature A during "of!" periods of the current and for thispililmflethebuckingwindingHonthelegli has been provided. In order to prevent this bucking coil H from bucking the buildingup of flux in the leg I), this bucking coil H has included in series therewith-a rectifier ra which allows current to flow only due to voltage induced in this coiluponadecreaseinfiuxoriginallycreated therein by the winding W by current derived through rectifier rl. In accordance with the present invention, and also the invention of said prior application, it is proposed to cause this bucking coll H not only to prevent the dropping of the armature A between two successive pulses of pulsating current but to also hold the armature A still slightly longer in its actuated position so as not to drop to its non-actuated position until during the second on. period of the pulsating current following deenergization of the winding w. Since the proper functioning of the special relay involves periods of delay the relay must of course be d and constructed in accordance with the frequency of the alternating current which it is to control and which controls such relay and in accordance with the present invention it is assumed that the alternating current to be employed is of a frequency of 60 cycles per second. In other words, the relay CPRA shown in Pig. 1 is constructed to close its contact I! during the first pulse of negative polarity following the first full pulse of positive polarity applied to its windingandsoastoopenthiscontact ll during the second wave of negative polarity following the last full pulse of positive polarity applied to its The relay CPRAI shown in Fig. 2 is of exactly the same wnstruction as the relay CPRA shown in Fig. 1 and therefore requires no further descriptlon ThereiayCPRBshowninFig. lisofexactly the same construction as that of the relay CPRA except that its winding W includes a rectifier 11 in series therewith which is poled in the opposite direction from that of the rectifier ri included inserieswiththewindingWofthemla CPRA. andfurtherdifiersfromtherelayCPRAbyhavin: the rectifier rb poled in the opposite direction from that of the rectifier ra included in the buckingcoilHoftherelayC'PR-A. Therelay 4 CPRBI of Fig. ii is of exactly the same constructionasistherelayCPRBof Fig. 1.

In both Figs. .1 and 2 the relays CPRA and CPRB are usedfor controlling the application of energy to a track circuit of a track section including track rails I insulated from an adjacent track section by insulating joints 2. It should. however, be understood that the invention is not limited to the application of current to a track circuit but may be usedto control any load circuit to which alternating current is to be applied and removed. It is desired to point out that the relay CP heretofore referred to as a control relay may be energized and deenergized intermittently to characterize a code and may therefore constitute a code repeating relay if a code type track circuit is involved.

Hg. 1 structure and operatimL-Referring to I Fig. 1 it will be observed that the contact I of the control relay CP when closed applies energy from the secondary winding of the transformer TI to the windings W-of both of the relays CPRA and CPRB and that byreason of the rectifiers ri and 1'! respectively included in series with these relays the relay CPRA is energized by pulsing current of positive polarity whereas the relay CPRB is energized by pulsing current of negative polarity. It is of course understood that the pulses of the first pulsating current each occurduring one-half of the alternating current cyclic whereas the pulses of the other pulsating current each occur during the other half of the alternating current cycle. In view of the construction of these relays as heretofore described the relay CPRA will close its front contact ll during the first negative pulse of the alternating current whereas the relay CPRB will close its contact ll during the first positive pulse of the alternat-- ing current after closure of the contact I. It will be observed that the two contacts II and ll of these relays are connected in multiple through branch circuit portions which include rectifiers rs: and 1-1! respectively. It will be observed that the rectifier 1': permits the fiow of current of positive polarity whereas the rectifier 11 permits the flow of current of negative polarity. Since, as already explained, the contact l0 closes or opens during a negative pulse of the alternating current only and since the rectifier rsvblocks the fiow of this current no sparking will occur at the ciionsi'act II when this contact is either opened or c Similarly, since the contact ll of the relay CPRB can close or open only during a positive pulse of thealternating current cycl and since the rectifier n blocks the fiow of current of positive polarity no current can fiow through contact ll during theinstantofits closureoropenins. From this consideration it should become apparent that no sparking at either of the contacts l0 or il'can occur during either closure or openingofthesecontacts. Itshouldfurtherbe observed that with both of the contacts II and i I closed alternating current fiows comparatively freelyfromthesecondarywindingofthetransformer Tl.

It will readily be understood from the foregoingdiscusionthattherehysCPRAandCPRB willalwaysbepickedupanddroppedinsequence and that this sequence depends upon at what ointinthecycleofthealternatingcurrentthe front contact I That is, if the first full pulse of current ppliedtotherelaylisapulaeofpositivepolarityt eplckingupoftherelayCPRAwiilpr-ecede that o! the picking up of the relay CPR-B, and vice versa. What has been said as to the sequential picking up of the relays CFRA and CPRB of Fig. 1 is likewise true of the sequential dropping of these relays in response to opening oi the contact 5 of the relay CP. It will be observed that a certain amount of resistance is imposed by the rectifiers r: and ry in multiple in the Fig. 1 structure, thereby causing heating of these rectiflers. It would be much more desirable to have one of the contacts It or II close the load circuit through a rectifier and to then have the other contact shunt out this rectifier, and such a construction is shown in Fig. 2 of the drawings.

Fig. 2 structure and peration.-In the modifled form of the invention illustrated in Fig. 2 the relays CPRAI and CPRBI are of th same construction as are the correspondingly designated relays of Fig. l but in this Fig. 2 structure the circuits are so organized that upon closing of the front contact 5 of the relay CP the relays CPRAI will always be picked up ahead of the relay CPRBI irrespectiv of the particular instant in a cycle of alternating current that this contact 5 is closed. The circuit organization is furthermore such that upon opening of the contact 5 the relay CPRBI is always the first one of these two relays to drop irrespective of the particular instant in a time cycle of the alternating current that contact 5 is opened. This picking up of the relays CPRAI and CPRBI in sequence in one order and the dropping of these relays in the inverse order irrespective of the instant of closure or opening of the contact 5 of the relay CP with respect to the cycle of the alternating current is accomplished through the medium of pick-up and stick circuits for the relay CPRAI presently to be described. By this construction, causing these relays to pick up in one orderand drop in the reverse order, it is possible to have the first relay to pick up to close a load circuit through a rectifier and to then have the second relay to pick up and shunt this rectifier, and to cause the opening of the circuit by first unshunting the rectifier and to thereafter open the circuit in which it is included.

Referring to Fig. 2 it will be observed that the relay CPRAI is provided'with a pick-up circuit including the front contact 5 of the control relay CP and the back contact 6 of the relay CPRBI, and that with the relay CPRAI once picked up it is stuck up through a stick or holding circuit including its own stick contact I and the front contact 8 of the relay CPRBI as soon as this latter relayhas assumed its energized position. It will also be seen that the picking up of the relay CPRAI in response to closure of the front contact 5 of the control relay CP results in the closure of an energizing circuit for relay CPRBI which includes both this contact 5 of the control relay CP and the front contact 9 of the relay CPRAI. This pick-up and this stick circuit each include the common return wire CW. In other words, the circuit structure for these relays CPRAi and CPRBI is such that upon closure of the front contact 5 of control relay CP an energizing circuit for the relay CPRAI only is closed and that this relay CPRAI upon picking up will close an energizing circuit for the relay CPRBI which will result in closing a stick circuit not including the contact 5, from which it is apparent that these relays will always pick up in the order CPRAI followed by CPRBI. It is also readily seen that with these relays both 6 assuming their energizing position the openinc or the contact 8 will directly break the energizing circuit for the relay CPRBI but that the relay CPRAI will remain energized through a stick circuit not including th front contact 5 of the relay CP. The stick circuit for relay CPRAI will therefore not be broken until the relay CPRBI has assumed its deenergized position. From this it is readily apparent that these relays will drop in the order CPRBI followed by CPRAI. In other words, these relays CPRBI and CPRAI are always picked up in the order CPRAI followed by CPRBI whereas they are always dropped in the order CPRBI followed by CPRAI. This particular sequence in the picking up of the relays CPRAI and CPRBI and the dropping of these relays in the reverse order is important because of the contacts l4 and I5 of these relays included in the load circuit. a

It will be observed that the picking up of th relay CPRAI may through the medium of its front contact l4 connect the secondary winding of th transformer T2 to the track circuit through the medium of the rectifier re and that this rectifier re may thereafter be shunted out by closure of the front contact i5 of relay CPRBI. As heretofore pointed out the contact I of the relay CPRAI closes only during a negative wave of the alternating current. It is readily understood that the closure of this contact I will occur at the time the rectifier re blocks the flow of current. After the contact has once closed pulsating current may how to the track circuit.

It will also be remembered that the front contact it: of the relay CPRBI which closes later than contact M will close only during a positive wave of the alternating current. This contact l5 therefore always closes during a positive wave of the alternating current and therefore only closes when current is free to flow through the rectifier rz so that the potential difference across the terminals of this rectifier rz is extremely low and cannot cause sparking at the contact Hi.

It will also be remembered from the foregoing consideration that the contact 15 of the relay CPRBI always opens prior to the opening of the contact M of the relay CPRAI and that this contact i5 only opens when current of positive polarity flows from the upper terminal of the secondary winding of the transformer T2 to the track circuit. Since the rectifier rz allows the free flow of this current of positive polarity the potential drop across this rectifier rz is very low and no sparking at the contact l5 upon opening of this contact will occur and that the opening of the contact I4 of the relay CPRAI can only occur when the upper terminal of the secondary winding of the transformer T2 is negative at which time flow of current in the load circuit is blocked by the rectifier 12: so that no sparking at the front contact I4 will occur upon opening of this contact.

The applicants have thus shown and described several embodiments of the present invention in one form of which an alternating current load circuit is closed through oppositely poled rectifiers included in multiple branches of this load circuit and in the other form of which a rectifier is temporarily included in the load circuit and it is desired to be understood that the invention is not limited to these embodiments and that various changes, modifications and additions may be made in practicing the invention without departing from the scope of the invention so long as these changes, modifications and additions come within the scope of the a nded claims.

What we claim as new is:

1. Apparatus for respectively closing and opening an alternating current load circuit wholly automatically by said apparatus in a manner to prevent sparking comprising, means including an asymmetric unit for closing a load circuit through such asymmetric unit at that part of a cycle of said alternating current when current flows in a direction so that the resistance imposed by said unit is a maximum and for thereafter wholly automatically closing a by-pass partial circuit around said unit at that part of a cycle of said alternating current when such current fiows in a direction so that the resistance imposed by said unit is a minimum, means including said means for opening said alternating current load circuit by inserting said asymmetric unit in said load circuit by removing such by-pass partial circuit at that part of a cycle of said alternating current when current fiows in a direction so that the resistance imposed by said unit is a minimum and n which then opens the said load circuit including said unit at that part of a cycle of said alternating current when current flows in a direction so that the resistance imposed by said unit is a maximum, and means for controlling both of said means by alternating current from the same alternating currentsource as that from which said load circuit is supplied.

2. Electro-responsive contact controlling means for controlling alternating current circuits comprising, a first polarity responsive relay controlled from an alternating current source and constructed to be slow acting and close and open a front contact when alternating current flowing from said source is of a polarity to flow in a particular direction irrespective of the time of closure or opening respectively of the control circuit for said relay, a second polarity responsive relay controlled from said alternating current source and constructed to be slow acting and close and open its front contact when alternating current flowing from said source is of the opposite polarity and irrespective of the time of closure or opening respectively of its control circuit, rectifying means, and a load circuit controlled by said two contacts and said rectifying means .and by alternating current from the same source by controlling two circuit portions in multiple one including one of said contacts and the other including the other contact, said contacts being closed in sequence and at times when current fiow due to said rectifying means in such portions is a minimum.

3. Electro-responsive apparatus for controlling an alternating current circuit, the combination with a source of alternating current, a first polarity responsive relay means controlled by current from said source and constructed to when energized from said source or deenergized irrespective of the time of energization or deenergization thereof with respect to a cycle of such current to close and open respectively a front contact thereof when the potential of said source is of a particular polarity, a second polarity responsive rela'y means controlled by current from said source and constructed to when energized from said source or deenergized irrespective of the time of energization or deenergization thereof with respect to a cycle of such current to close and open respectively a front contact thereof when the potential of said source is of the reverse source including relay retarding means to cause it when energized from said source or deenergized irrespective of the time of energization or deenergization thereof with respect to a cycle of such current to close and open respectively a front contact thereof when the potential of said source is of a particular polarity, a second relay controlled by current from said source including relay retarding means to cause it when energized from said source or deenergized irrespective of the time of energization or deenergization thereof with respect to a cycle of such current to close and open respectively a front contact thereof when the potential of said source is of the reverse polarity, a controlled circuit having two branch paths in multiple one of which includes a rectifier the flow of current wherein is controlled by one of said front contacts and the other branch of which includes the other of said front contacts, whereby upon energization of said relays the controlled circuit is first closed by one contact through a rectifier while such rectifier is blocking the fi'ow of the initial current and such rectifier is then by-passed by the other contact while said rectifier passes current and upon deenergization of said relays the controlled circuit is first partially opened by opening such by-pass at a time when such rectifier is passing current and is then fully opened by opening the branch including said rectifier at a time when such rectifier is blocking current.

5. Apparatus for closing an alternating current load circuit in a manner to prevent sparking comprising, a first means for closing a load circuit through an asymmetric resistance unit at that part of a cycle of alternating current when the asymmetric resistance unit restricts the fiow of current therethrough, other means for thereafter closing a shunt solely around said asymmetric resistance unit at that part of a cycle of the alternating current when the asymmetric unit is allowing the substantial free fiow of such current, and means for controlling said first means and said other means by alternating current from the same source as that from which said load circuit is supplied.

6. Apparatus for opening an alternating current load circuit in a manner to prevent sparking comprising, means for inserting an asymmetric resistance unit in said load circuit by removing a by-pass circuit portion from immediately around such asymmetric resistance unit at that part of a cycle of said alternating current when the asymmetric resistance unit allows the sub- 7. Apparatus for closing a circuit for the fiow of alternating current with reduced sparking comprising, a first polarity responsive relay constructed to be actuated rapidly the instant the magnetism in its core structure has built up to a predetermined value in a particular direction, a second polarity responsive relay constructed to be actuated rapidly the instant the magnetism in its core structure has built up to a predetermined value in the opposite polarity direction, means for at times applying alternating current from such source to said relays to cause them to assume an actuated position in succession, said relays by reason of their polarity responsive character being operated sequentially time spaced substantially a half cycle of said alternating current in a manner such that one relay closes its contact when current from said source flows in one direction and such that the other relay closes its contact when current from said source flows in the opposite direction, an energizing circuit for said second relay including a contact closed only when said first relay assumes an actuated position, a load circuit including a front contact of said first relay and an asymmetric unit in series therewith poled to restrict the flow of current when the front contact or said first relay is first closed and a front contact of said second relay in multiple with said asymmetric unit.

8. Apparatus for closing a circuit for the fiow of alternating current with reduced sparking comprising, a first relay constructed to be actuated rapidly the instant the magnetism in its core structure has built up to a predetermined value and including an asymmetric unit in series with its winding, a second polarity responsive relay constructed to be actuated rapidly the instant the magnetism in its core structure has built up to a predetermined value and including an oppositely poled asymmetric unit in series with its winding, means for at times applying alternating current from such sourc to said relays to cause them to assume an actuated position in succession, said relays and their associated asymmetric units by reason of their polarity responsive character being operated sequentially time spaced substantially a half cycle or said alternating current in a manner such" that one relay closes its front contact when current from said source flows in one direction and such that the other relay closes its front contact when current from said source flows in the opposite direction, an energizing circuit for said second relay including a contact closed only when said first relay assumes an actuated position, a load circuit including a front contact of said first relay and an asymmetric unit in series therewith poled to restrict the fiow of current when the front contact of said first relay is first closed and a front contact 01 said second relay in multiple with said last mentioned asymmetric unit.

MARCIAN A. SCHEG. OSCAR H. DICKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

